Voiced dental and alveolar taps and flaps
The voiced alveolar tap or flap is a type of consonantal sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents a dental, alveolar, or postalveolar tap or flap is ⟨ɾ⟩.
The terms tap and flap are often used interchangeably. Peter Ladefoged proposed the distinction that a tap strikes its point of contact directly, as a very brief stop, and a flap strikes the point of contact tangentially: "Flaps are most typically made by retracting the tongue tip behind the alveolar ridge and moving it forward so that it strikes the ridge in passing." That distinction between the alveolar tap and flap can be written in the IPA with tap ⟨ɾ⟩ and flap ⟨ɽ⟩, the 'retroflex' symbol being used for the one that starts with the tongue tip curled back behind the alveolar ridge. The distinction is noticeable in the speech of some American English speakers in distinguishing the words "potty" (tap [ɾ]) and "party" (flap [ɽ]).
For linguists who make the distinction, the coronal tap (as in Spanish pero) is transcribed with ⟨ɾ⟩, and the flap (as in American English ladder) is transcribed with a non-IPA symbol ⟨ᴅ⟩ (not to be confused with the IPA symbol ⟨ɒ⟩, which stands for the open back rounded vowel). Otherwise, alveolars and dentals are typically called taps and other articulations flaps. No language contrasts a tap and a flap at the same place of articulation.
The sound is often analyzed and thus interpreted by non-native English-speakers as an 'R-sound' in many foreign languages. In languages for which the segment is present but not phonemic, it is often an allophone of either an alveolar stop ([t], [d], or both) or a rhotic consonant (like the alveolar trill or the alveolar approximant).
If the alveolar tap is the only rhotic consonant in the language, it may be transcribed with ⟨r⟩ although that symbol technically represents the trill.
The voiced alveolar tapped fricative reported from some languages is actually a very brief voiced alveolar non-sibilant fricative.